Electrical sound reproducing process



July 28, 1931. A. J. CAWLEY 1,816,360

ELECTRICAL SOUND REPRODUGING PROCESS.

Filed Jan. 8. 1921 -munmmmmummusw1mm Patented A July 28, 1931 UNITED STATES PATENT OFFICE .unYsIUs J.-

CAW'LEY, OF NEW YORK. N. Y., ASSIGNOR TO RADIO CORPORATION OF AMERICA, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE ELECTRICAL SOUND REPRODUGING PROCESS Application filed January 8, 1921. Serial No. 435,983.

The invention relates generally to sound recording; more particularly it is concerned with a means of direct electrical reproduction of sounds from a photographic record. The ordinary photographic sound record requires for its electrical reproduction the use'of aselenium cell, or its equivalent, and a heat absorbing means; a light is also necessary for the operation of the cell. Such devices are expensive and require considerable attention to keep them in proper condition. In this process they are replaced by a simple contact device, requiring little or no attention on the part of the operator.

Although the above devices are dispensed with, still the method of reproducing described possesses all of the advantages usuall ascribed to them. For instance, the scratc ing sounds'of a mechanical reproduction are eliminated.

A special means of providing a sound record that is longitudinally condensed and of no greater width than that of the ordinary motion picture film, is also described, an attempt being thus made to adapt a sound record taken at high speed to the lower standard film speed.

A special type of sound recorder, which is designed in such a manner as to increase its sensitiveness above the ordinary is also de-. scribed.

The invention is not limited to producing a combined picture and sound record that may be electrically reproduced, as a sound record alone may be obtained, if desired.

Reference is to be had'to the accompanying drawings forming a part of the specification, in which like characters of reference denote corresponding parts in all the views, and in which,

Figure 1 is a view of a negative film having a photographic sound record on its margin.

Figure 2 is a view of a special electrically conducting sound record, which is to be attached to film margin.

Figure 3 is a view of the positive film with its special sound record attached to its margin passing through part of a projector.

Figure 4: is a detailed view of the brush, or contact member.

trically,

Figure 5 is a. view of the positive film carrying its sound record, together with the contact members and their associated electrical paratus used in producing a longitudinally reduced sound record.

The sound record is photographed in the camera in the well-known manner of varying the light intensity, the result being a record consisting ofa broad band having varying amounts of metallic silver. This record is preferably juxtaposed to the picture record and forms one piece with it. This is shown at B in Figure 1, where A is the film.

In order to obtain the reproducing sound record, thin metallic foil is provided with a photosensitive coatin If desired, this can be done on a large sca e. For instance, large sheets of copper are plated with silver elecand the silver surface in turn coated with bromine and iodine/thus partly converting it into a bromide and iodide of silver, as in the daguerreotype process. The sheets of foil may be then cut into long narrow tapes. These tapes are attached to the mar in of the positive film preferably after they ave been printed under the negative sound record and developed. When such a strip is printed and then developed with mercury vapor in the usual manner, the result is a photographic copy consisting of a varying amount of an amalgam imbedded in a metallic surface. Such a photographic copy will be able to withstand considerable wear, as for instance that due to the passage over it of the brush hereinafter described. This strip is attached to the margin of the developed ositive, so that when the latter is fed throug the projector, as shown in Figure 3, a brush 2 carrying suitable contacts rests against the metallic tape as it passes over the sprocket 3, which-may be located at any part of the projector, but is here shown to be the one which is placed just before the loop 25, situatedadjacent to the film gate; this sprocket has a continuous motion. It is to be understood, however, that One can readily see that the current passes through Eli the photographic record, and is varied in its intensity corresponding to the amounts of amalgam contained thereon. Mercury is quite well adapted to accomplishing this, because it possesses one of the highest electrical resistances of the I metals.

A detailed View of One form of the brush is shown in Figure 4, where 4; and 4 are the contact blades, attached firmly to the insulated or insulating supports 5. This support is preferably made of wood, but may be of metal properly insulated. The wires 6 and 6 lead to the reproducing apparatus.

Another view of the reproducing system is shown in Figure 5, where 7 is a source of power, such as a battery or dynamo, 8 an induction coil, and 9 an amplifier such as an au dion. The arrangement is such that the more or less feeble "ariations in the amplitude of the electrical current, which are caused by the sound record, are amplified by the induction coils and associated audion in such manner that electrical fluctuations are greatly magnified.

This process reduces the sound reproduction in the projector to the simplest possible. A light source with its electrical circuit, selenium cell and heat-absorbing means are eliminated, as is also the requisite attention on the part of the operator.

There is also another advantage. If the picture and sound records are made on separate films, the latter moving at a much greater speed than the former, a longitudinally condensed record may be made from the sound record which may be attached to and run at the same speed as the positive picture record. In order to accomplish this, a special printing device is used, as shown in Figure ,6. This consists of a gear wheel 15 carrying or moving the metallic sound record strip and connected by the intermediate gear wheel 17 to wheel 16, which moves the original sound record tape. The gearing is so adjusted that tape 18 moves say one sixth as fast as the original sound record 526, if the ratio of the recording speed to that of the reproducing speed is six. 19 is a cylindrical lens, or other optical arrangement for properly concentrating the light coming through the aperture 20, from light source 21. The metallic film is therefore moved much more slowly than the negative, with the result that it will be much shorter than the latter, but will contain all of the sound record in a much more concentrated form; in other words the original record is longitudinally reduced. If desired, the film may be fed in an intermittent manner, instead of continuously as shown, just as is done in the ordinary picture printer. After developing and fixing, this tape is cemented to the margin of the positive film in the usual manner.

It IS obvious that no material alteration need be made to the ordlnary motion picture machine as it exists in practice, it being only necessary to attach the brush to the framework of the projector at any desired point, and lead the connecting wires to the reproducing apparatus situated mostly at the pro jecting screen. The film can pass through It is not absolutely necessary to coat the,

plate with silver, as mercury pictures of the type described have been produced dlrect- 1y upon copper.

Obviously, other photosensitive surfaces may be used besides that mentioned. The main point to bear in mind is that a vary ng resistance is thereby offered to a traverslng electric current in the moving film.

In developing the strip, a porous ribbon may be impregnated with mercury vapor, such as by leaving it in an enclosed space containing heated mercury, so that when taken out, it will evolve mercury vapors at its surface. Slight heat will then generate suflicient vapor. It is to be remarked-that since the porous ribbon and metallic surface are inecontact, a comparatively slight amount of vapor will accomplish the desired result. By winding the porous strip and exposed photosensitive surface together on a reel or drum, and leaving them in contact for a sufiicient length of time, the vapors will develop the picture. A similar tape containing fixing solution may be used in like manner to fix the record.

There are many other ways of producing a sound record that may be reproduced electrically without a selenium cell, without departing from the spirit of the invention. I

Having thus described my invention, claim as new and desire to secure by Letters Patent,

1. An all metal electrically conducting photographic sound record, capable of electrical reproduction.

2. A metallic strip bearing a photographic sound record consisting of an amalgam capable of varying an electrical current.

3. An electrically conducting strip carrying a photographic sound record capable of varying an electric current.

4. A film containing electrically conducting particles having a metallic conducting strip attached to its margin, said strip bearing a photographic sound record capable of varying the intensity of a traversing electric current.

5. A film having an electrically conducting strip of metal bearing a metallic, longi- 5 tudinally reduced photographic sound record attached to its margin for the purpose of producing synchronous sound and picture records.

6. A metallic electrical conducting sound record which is a longitudinally reduced photographic copy of a record made photographically at a higher speed.

7. A sound recording process consisting in making a photographic sound record at a speed greater than standard motion picture speed and printing a longitudinally reduced copy of said record.

- 8. A sound recording process consisting in printing a sensitive film moving at a slower rate than that at which a master record moves to produce adevelopable sound image which is longitudinally reduced while its width remains constant.

9. A process of producing a photographic sound record which consists in printing upon a photosensitive surface a copy of a master sound record, and developing said surface by placing a porous layer saturated with developing elements upon said sensitive surface to chemically alter said surface.

10. A process of producing a talking picture record consisting in rinting a co y of a master sound record p otographical y on the margin of a motionpicture film and developing said surface by placing a porous layer saturated with develo ing agents upon said surface'to chemically alter the substance of said margin.

ALOYSIUS J. CAWLEY.

CERTIFICATE OF CORRECTION.

.Patent No. 1,816,360. Granted July 28, 1931, to

ALOYSIUS J. CAWLEY.

it it hereby certified that the above numbered patent was erroneously issued to "Radio Corporation of America, of New York, N. Y. a corporation of Delaware", as assignee of theentire interst in said invention, whereas said patent should have been issued to the inventor, said Gawley, as sole owner of said invention; and that the said Letters Patent should be read with this correction therein that the same may conformto the record of the case in the Patent-0ifice.

Signed and sealed this 29th day of September, A. D. 1931.

. M. J. Moore, (Seal) Acting Commissioner of Patents. 

